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Catalisadores NiMoS suportados em sílicas mesoporosas ordenadas para a hidrodessulfurização de organossulfurados refratários: efeito do ácido oxálico como agente quelante e avaliação de fases ativas
(Universidade Federal de São Carlos, 2024-07-19) Albuquerque, Jonas Santana; Urquieta-González, Ernesto Antonio; https://lattes.cnpq.br/2389975677904655; https://orcid.org/0000-0001-5141-6004; https://lattes.cnpq.br/9732884471657315; https://orcid.org/0000-0003-1214-8742; Batista, Marcelo da Silva; Nogueira, Francisco Guilherme Esteves; Santos, João Batista Oliveira dos; Zapelini, Iago William; https://lattes.cnpq.br/1573905329100173; https://lattes.cnpq.br/8117497993539795; https://lattes.cnpq.br/0285313473901330; https://lattes.cnpq.br/2130645530441578; https://orcid.org/0000-0002-3646-8612; https://orcid.org/0000-0002-6268-0342; https://orcid.org/0000-0002-8872-0410
In the last decades, regulatory agencies have been establishing stricter specifications for fuels in relation to the emission of pollutants and, especially, the sulfur content. Therefore, hydrodesulfurization (HDS) is an essential step in oil refining for the production of fuels with a low content of organosulfur compounds, respecting the specifications proposed by current legislation. Conventional catalysts are based on metal sulphides of NiMo supported on alumina, however, due to its low hydrogenating capacity and strong metal-support interaction, HDS of refractory organosulfur becomes limited. Seeking to minimize these limitations, the objective of this work was the study of catalysts, supported on mesostructured silicas, with subsequent evaluation in the HDS reaction of dibenzothiophene and 4,6-dimethyldibenzothiophene. Different methodologies for the synthesis of mesostructured supports (SBA-15, SBA-16 and Al-SBA-15) and the influence of using oxalic acid as a chelating agent on the impregnation of the nickel precursor were evaluated in this sudy. Results show that mesostructured supports with optimized textural properties and moderate Brønsted acidity play an important role in obtaining highly active catalysts for HDS of refractory compounds. The use of oxalic acid generated nickel oxalate complexes with low interaction with molybdenum, increasing the dispersion and formation of the MoS2 active phase, especially in catalysts supported on Al-SBA-15. All oxide precursors with oxalic acid, (Ni-AO)Mo, showed reduction peaks at lower temperatures and hexacoordinated molybdate species with octahedral geometry (Mo (Oh)). The NiMoS/Al-15 and (Ni-AO)MoS/Al-15 catalysts presented the highest DBT conversions, while the NiMoS/15 catalyst was considered the most promising for the HDS of 4,6-DMDBT, as it presented the highest hydrogenating capacity, better dispersion of the active phase and total conversion of the organosulfur compound into desulfurized hydrocarbons. Finally, the (Ni-AO)MoS/Al-15 catalyst achieved conversions above 90% at the end of the 8 h reaction of the third reuse cycle, showing that no apparent deactivation occurs.
Análises térmicas em sistemas poliméricos: uma ferramenta para a avaliação da degradação
(Universidade Federal de São Carlos, 2024-07-19) Lopes, Jameson Santos; Cruz, Sandra Andrea; https://lattes.cnpq.br/9632409046763256
In the contemporary world, the demand for polymeric materials has grown intensely to meet the pace of consumption. In view of this, concern about the disposal of polymers becomes an issue when considering waste management. Thus, investigating the impact of degradation on the physical and chemical properties of these materials by means of thermal analyses is a possible approach to this problem. To accomplish this, this study was structured to introduce basic concepts on the subject as well as address the degradation mechanisms undergone by polymers and their precursor agents, refer to the impacts of degradation on the properties of some polymeric systems, and discuss the fundamentals, characteristics, and parameters of thermal analyses. Thermal analyses are a group of various techniques that measure the physical and chemical properties of a given material as a function of temperature under controlled atmospheric, heating and cooling conditions. The properties of the sample are analyzed by monitoring the changes in the material as a function of time and temperature compared to a reference, which makes it possible to determine certain physical and chemical properties of the material in order to determine its possible applications, storage, behavior, and transport. For this work, the focus will be on Differential Scanning Calorimetry (DSC) analyses, which monitor the flow of heat through the sample over time and temperature. With DSC it is possible to determine the Vitreous Transition Temperature (Tg), Crystaline Melting Temperature (Tm) and Crystallization Temperature (Tc), the melting enthalpy (∆Hf), degree of crystallinity (Xc), specific heat, phase transition, curing and crystallization kinetics. And Thermogravimetric Analysis (TGA), which relates the change in mass in a sample under a controlled atmosphere; it investigates the thermal decomposition profile of the material. With TGA, we can study the thermal stability of the sample, thermal decomposition, moisture content and pyrolysis of certain substances. This work will conclude with a discussion of two case studies. The first one will address the use of thermal analyses to understand the effects of degradation on Nylon 6,6, while the second will investigate the durability of cables in nuclear plants.
Agroecologia e construção do conhecimento: um estudo de caso da práxis da Comunidade que Sustenta a Agricultura (CSA) Sorocaba
(Universidade Federal de São Carlos, 2024-07-19) Souza, Thais Santos de; Franco, Fernando Silveira; Lattes: http://lattes.cnpq.br/3218633711361955; Duval, Henrique Carmona; https://lattes.cnpq.br/1127516712972199; https://lattes.cnpq.br/0487673913150466
Agroecology is built on the valorization of knowledge, respectful relationships between all beings, solidarity economy and the focus on conservation and management of biodiverse agroecosystems. Aligned with Agroecology, the global organization Community that Sustains Agriculture (CSA) emerged in the 1960s, which seeks actions of solidarity, collaboration and affection, through the fair marketing of quality food. In recent years, CSA have grown in several Brazilian municipalities, associated with principles that dialogue with agroecology. The central objective of the work is to study the communication strategies and construction of agroecological knowledge that occur through the Community that Sustains Agriculture (CSA) based on the case study of CSA Sorocaba, located in the state of São Paulo. The approach used is action research, using active methodologies, semi-structured interviews and focus groups. As a result, the aim is to systematize the experience, outlining strategies that allow the future exploration of the power of agroecology in the reconstruction of a critical, humane, transformative science aligned with popular principles.